tailshafts ppt

PROPULSION DEVICES AND PROPELLER SHAFT

Various propellers and propulsion devices for large and medium size ships are discussed here. The hydrodynamic design part is short. Main attention is given to engine room design and

Pentti Häkkinen chapter 2Wärtsilä New professionals 3. – 7.11.2008

attention is given to engine room design and operation aspects.

PROPULSION DEVICES AND PROPELLER SHAFT

The efficiency is obtained with large, slow turning propeller.

Diameter is restricted by: •Clearance between tip and hull •Pressure pulses•Submerge in ballast conditions (mainly for oil tankers)•Rev. speed of direct coupled low

Power demand kW


•Rev. speed of direct coupled low speed engine (seldom) •In few merchant ships propeller reaches below ship base line (excpetion GTS Finnjet 0.5 m)

To the right traditional thumb rule

Propeller rev. speed rpm

10 %

3 %

Power demand 1 CARGO SHIP MAIN DIMENSIONS

CB LPP / m

0.8

0.7

250

200

T / m B / m

LPP / m

60

50

40

20

15


MAN-B&W Engine Selection Guide.

10000 20000 30000 50000 dwt

0.6

0.5

150

100

50

B / m

T / m

CB

40

30

20

10

10

5


Shaft power MW

16

15

Vessel speed kn

35

30

25

20



2000 5000 10000 40000 80000 dwt

15

14

13

15

10

5

2


Shaft power kW

Propeller diameter

m

35

30

25

20

8.58.07.5

7.06.5

6.0



50 60 70 80 90 100 110 130 150 190 rpm

15

10

5

2

6.0 5.5

5.04.5

SHAFTLINE

One or several intermediate shafts and one propeller shaft.

Generally horizontal line, sometimes rising to foreship direction. Shafts in twin propeller ship are seldom parallel.

Shaft diameter calculated on class equation. Material and ice class influence here.


Sterntube includes propeller shaft bearings. Practically always plain bearings with either water or oil lubrication.

Seals at both sterntube ends. They allow relatively large shaft movements. Tightness in confirmed when pressure difference between inside and outside remains inside limits (about 0.4 bar).

Shaftline must be removable for inspection and replacement of seals and bearings. Withdrawal either inside or outside.

Stern tube of a twin screw ship

Bracket Sterntube located inside protective tube

Bulkhead

Bored (hollow) shaft

Flangeless coupling

Fore sterntube bearing


Aft seal Fore sealAft stertube bearingEngine room aft compartment

5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Stern tube lubrication oil system

Header tank

Connection to cold water line

Pumps of taking oil sample from sterntube and bilge

Expansion line

Pressure line


Transfer pump to storage tank

Oil tank

Header tank fill pumps

Sterntube bearing

Integrated oil system for stern tube and seals

Compressed air supply Pressure control

Return lines separate for detection of water and metal residues. Aft seal can be connected to 2 separate header tanks so that pressure difference over seal lips is approx. 0.3 bar.

Header tanks for bearing

Header tanks for fore seal

Header tanks for aft seal

Ventilation Ventilation


Aft seal Bearing Fore seal Oil return

Lip seals, oil feeding and seal assembly

Propeller boss

Fastening of protection liner

Screws for lip carrier

Wear down-meter installed in oil chamber.

Oil is fed through bore channel at top, returned through bore channels at bottom.


Conus O-ring Chromium liner Propeller shaft Rubber seal Tension spring

Lip type aft seal

Compressed air feeding used to prevent ingress of sea water.


Combination of lip and face seal

Coast Guard-name refers generally to seal assembly where the slightest oil leak to sea can be readily detected and prevented.


Face seal

Cedervall seal has mating surfaces of cast iron and ceramic material. They are pressed together by compression


together by compression springs behind the rotary member. Springs permit some axial shaft movement

Hydraulically installed flangeless shaft coupling

Thick liner with internal conus is forced around the thin liner with external conus. The axial force is created hydraulically. After relase of hydraulic pressure the torque is transmitted by friction.

Assembly screw Oil feed Lube oil feed Internal liner


Hydraulic nut Cylinder ring Shaft ends External liner Assembly support

Hydraulically tensioned and installed screws

Hydraulic pressure stretches the screw and simultaneously reduces the external diameter. In this state the nut is

Hydraulic pressure Tool stretching the screw Shaft or the piston

Nut


this state the nut is installed. At relief of oil pressure the screw is expanding and compresses to the flange bores. The hydraulic tool is then removed.

Bore and screws machined with tight tolerances.

After the assembly has been completed

Sterntube bearing No bearing metal lining in the way of oil feed channels

R

P

B

K

JA

M

O

N

CF


5

2°

20

45°D

*) Aft bearing: 1,5 … 2 x A, Fore bearing: 0,5 … 0,8 x A

A B C D F J K M N O P R200-299 min. 28 * 4 25 35 10 80 95-240 25 3 70-100300-399 min. 30 * 4 25 40 10 80 170-340 25 3 105-135400-499 min. 33 * 4 25 45 10 80 245-440 25 3 140-170500-699 min. 36 * 4 25 50 10 110 290-515 35 3 175-205700-900 min. 40 * 4 25 55 10 140 410-785 35 3 245-315

Effective bearing length

Normal supper bearing model

Bearing frame and slide shells have horizontal division at shaft centre height.

Often the support of

Free oil circulation, ring cathes some oil from surface and allows it to flow through hole at top.

Seal rings at both ends.


Oil reservoir inside pedestal with water cooling coil.

Often the support of slide shells has spefical outside which can accommodate some alingment deviations.

Seal rings at both ends.

Hydraulic propeller mounting method

Propeller

Cast iron liner baked inside the propeller special requirement in case when torque variation was high.

Chromium protective liner

Hydraulic nut

Threaded end section


linersection

Protective coverl

Oil supplyLubrication oil supply

Conical shaft end in way of propeller

Blade pitch setting mechanisms

Slide mechanism requires higher axial force than connecting rod mechanism Axial force required to turn

the blade N/Nm

12

10

8


60 40 20 0 20 40 60Astern Ahead

Blade pitch position (degrees)

Normal operation range

8

6

4

2

Mechanisms

Connecting rod Crank-pin Slot-pin


Servo valve in the oil distribution box / in the hub

Piston movement

Ahead

Indication

OD-box borders

Rotating shaft

Servo valve

Volume af piston back side always

In the OD box


Bore oil channels

Servo valve moves together with the high pressure pipe

Oil pump

High pressure oil inside the inner tube, low pressure return oil around it

Ahead

OD-box bordersVolume af piston back side always connected to inner tube oil pressure

In the hub

Main cylinder inside the bullwheel

Oil feed pump


Servo valve and working piston travel connected to the push rod.

Inside the propeller hub only the cross head (moved by push rod) and some lubrication oil. Main piston inside bullwheel

1. Blade

2. Fastening screws

3. Sealing ring

4. Support and turn ring

5. Hub frame

6. Piston

7. Cylinder

KaMeWa type propeller hub


7. Cylinder

8. Protection cover

9. Feed valve

10. Cross head

11. Pin

12. Slide

13. Turning pin

14. Relief valve

15. Shaft flange

Oil Distribution (OD-box) unit on the shaft

Servo valve is moved bu the tubular shaft extending to propeller hub. Mechanism requires a weakening cut in the shaft. High pressure oil always inside inner tube.

16. Intermediate shaft

17. Valve stem

18. Aft wall

19. Servo motor


20. Low pressure seal

21. High pressure seal

22. Mobile lever

23. Push rod lever

24. Frame of OD unit

25. Stand by servo

26. Relief and safety valve

Gap and Sag values

Gap and Sag are used to bring mating flanges in correct (calculated) position before fastening nuts. The shaft are rotated and dial gauge reading during the full circle indicated the position.

Gap is positive when opening in the lower side is bigger that in the

m

a


side is bigger that in the upper side = n - m

Sag is positive when propeller side (here left) flange is in higher position. = a

n

Alignment procedure, Gap and Sag values

Fastening of the flanges proceeds from propeller side to the engine. Vertical position of each bearing is adjusted so that calculated gap and sag values are obtained.

The shaft is slightly hanging between the bearings. The shaft is never straight line. Optimal bearing position can be also outside of the theoretical straight line.

Deviations in the figure below are exaggerated.


Deviations in the figure below are exaggerated.

Alternative method is to measure the vertical load at each bearing and compare with calculated values.

Alignment of the crank shaft

Crank shaft is rotated and the distance between crank webs measured in five positions. This gives reliably the reading difference between top and bottom position. Possible crankshaft bending due the engine frame deformation is vertical direction (also transversal) is obtained.


Big deviation indicated that engine frame for some reason has been excessively bent. Slight ’catback’ is normally beneficial.

Mechanical rudder propeller (Z-drive)

Vertical shaft has strong support to accpet thrust form all direction. Shaft bearings are connected


bearings are connected to to a block, welded in ship hull. Seals prevent sea water ingress.

Mechanical rudder propeller (Z-drive)

Rudder propeller and main engine often in inclined position.


Cardan hinges allow a lower main engine position. Hinges should have equal angles.

Pitch control mechanism in Z-drive unit

Main piston, here bowl-

Roller bearing located close to the bevel gear wheels.


here bowl-type directly connected to cross head.

Servo valve allows high pressure oil to fore or aft side on main piston

Thrust bearing

Azipod electric azimuthing propeller

Hydraulic moduleSlip rings

Air channel

Air cooling Runko-osa

Hydraulic slewing


Radial bearing and shaft seals

Axial and radial bearings

Electric motor

Hydraulic slewing motor

Azipod electric azimuthing propeller

Eralier reliability problems have been solved, but ABB Azipod is now the only pod in the market. High capital cost is the main drawback.

Shaft seal mainentance in


mainentance in drydock

Voith-Schneider propeller

Voith-Schneider is the only maker or vertical shaft propellers, so called trochoid propeller. Two vertical shaft propellers are still a popular solution for tugboats, even if expensive and heavy construction. Low acoustic emission is asset in naval craft.


Voith-Schneider propeller thrust


The entire unit rotates around the vertical axis. By moving the joint end on link shaft, stepless thrust to any direction can be created.

tailshafts ppt

Documents

wrtsil new professionals

propeller shaft bearings

twin propeller ship

engine room design

merchant ships propeller

manbw engine selection

oil lubrication

shaft diameter